Serum Levels of Interleukin-18 Are Elevated in the Subacute Phase of Kawasaki Syndrome

Background: Elevations of various cytokines, including Th1 and Th2 cytokines, have been reported in the acute phase of Kawasaki syndrome (KS). As interleukin (IL)-18 plays an important role in the Th1 cell response, investigating the relevance of IL-18 in KS should be helpful in determining the pathophysiology of KS. Therefore, we examined the IL-18 values in KS. Methods: Serum IL-18 values were measured by an enzyme-linked immunosorbent assay. Samples were obtained from 41 patients in the acute and subacute phase of KS, 35 age-matched febrile controls and 13 afebrile controls. Results: No difference was observed in the values of white blood cell counts or C-reactive protein between acute-phase KS patients and febrile controls. On the contrary, acute-phase KS patients showed a significantly lower mean IL-18 value (398 ± 206 pg/ml) than that of febrile controls (584 ± 307 pg/ml) (p = 0.006). Subacute-phase KS patients showed a significantly elevated level of IL-18 (517 ± 276 pg/ml) compared to acute-phase patients (p = 0.0008). The IL-18 values in the subacute-phase patients showed a significant positive correlation with the duration of fever (r = 0.427, p = 0.0055) and also with the presence of coronary artery abnormalities (r = 0.332, p = 0.0340). The incidence of elevated IL-18 values in the subacute-phase patients was significantly higher than that in the afebrile controls (p = 0.048). Conclusions: Patients with KS showed normal IL-18 values in the acute phase and elevated values in the subacute phase. IL-18 pathways were activated in the subacute phase of KS, and subacute IL-18 values might be reflected in the severity of KS.